This module instantiates the Proof framework for
constructing proofs over RDFGraph expressions.
The intent is that this can be used to test some
correspondences between the RDF Model theory and
corresponding proof theory based on closure rules
applied to the graph, per http://www.w3.org/TR/rdf-mt/.

Make an inference rule dealing with RDF instance entailment;
i.e. entailments that are due to replacement of a URI or literal
node with a blank node.

The part of this rule expected to be useful is checkInference.
The fwdApply and bwdApply functions defined here may return
rather large results if applied to graphs with many variables or
a large vocabulary, and are defined for experimentation.

Forward and backward chaining is performed with respect to a
specified vocabulary. In the case of backward chaining, it would
otherwise be impossible to bound the options thus generated.
In the case of forward chaining, it is often not desirable to
have the properties generalized. If forward or backward backward
chaining will not be used, supply an empty vocabulary.
Note: graph method allNodes can be used to obtain a list of all
the subjects and objuects used ina graph, not counting nested
formulae; use a call of the form:

Make an inference rule dealing with RDF subgraph entailment.
The part of this rule expected to be useful is checkInference.
The fwdApply function defined here may return rather large
results. But in the name of completeness and experimentation
with the possibilities of lazy evaluation, it has been defined.

Backward chaining is not performed, as there is no reasonable way
to choose a meaningful supergraph of that supplied.

Make an inference rule dealing with RDF simple entailment.
The part of this rule expected to be useful is checkInference.
The fwdApply and bwdApply functions defined return null
results, indicating that they are not useful for the purposes
of proof discovery.